UK researchers have looked at alginates that occur naturally in “kelp” seaweed (the variety that resembles large blades). They found that these alginates may help reduce the amount of fat the body digests.

Their study showed that, in the lab, certain types of alginates can slow down the enzyme activity of a fat digesting enzyme called pancreatic lipase. The researchers believe that if the alginates can block this enzyme, less fat would be absorbed by the body, which would stop people becoming obese.

However, the research did not draw any definitive conclusions, the most pertinent being that weight loss would not necessarily occur in humans (or even in mice). It's also unclear whether any potential effect from seaweed extract would lead to an improvement in weight-related health issues, such as reduced risk of diabetes.

Even if the alginates studied were successful in achieving weight loss, this does not mean they are safe to consume. Ultimately, ingesting a substance that slows down fat absorption is unlikely to have the same health benefits as a well-balanced diet and exercise – this is a tried and tested lifestyle choice for maintaining a healthy weight.

Nonetheless, the market for quick-fix weight loss treatments is large and extremely profitable, so research into seaweed extract will almost certainly continue.

Blocking fat not always good

Fats play an important role in metabolism; it’s just the intake of excessive fat that is a health problem. This means that the potential for alginate to stop excess fat being absorbed by the body has its downsides, and the excess fat will have to come out in some capacity.

Weight loss drugs such as orlistat work on a similar principle, and have numerous side effects, including oily diarrhoea, flatulence and a sudden urge to pass stools.

Where did the story come from?

The study was carried out by researchers from Newcastle University and was funded through a BBSRC CASE studentship (a grant programme for bioscience researchers) with industrial sponsors Technostics Ltd.

The study was published in the peer-reviewed science journal Food Chemistry.

The UK media’s reporting of the study was generally accurate, though much of the reporting gives the impression the alginates studied had proven to be an effective weight loss supplement in humans.

What kind of research was this?

This was a laboratory study investigating how a compound called alginate could influence the digestion of fat.

Alginates are chemicals that can be extracted from the cell walls of brown seaweed or from certain bacteria. Using alginate as a food additive is not a new concept, but this latest news covers new territory: their potential as an anti-obesity treatment.

In industrialised countries, dietary fats can account for 40% of energy intake, with triacylglycerol (TAG) being the major component. An enzyme called lipase, excreted from the pancreas, plays an important role in the digestion of fats in the body, so reducing pancreatic lipase activity would reduce fat breakdown, resulting in lower amounts being absorbed by the body. This would mean the fat passes straight through the body and wouldn’t accumulate under the skin or around organs, which is bad for your health.

Laboratory research like this is useful for establishing proof of a particular concept, but many more tests are needed for potential food additives. Experiments on humans are more important and would provide more information about the potential risks and rewards of using alginate as a food additive or a weight loss agent.